Immune Sensing of Latent Cytomegalovirus Reactivation: Impact on Immune Senescence?

Immune Sensing of Latent Cytomegalovirus Reactivation:Immune Sensing of Latent Cytomegalovirus Reactivation:Impact on Immune Senescence?Impact on Immune Senescence?

Molecular Virology Lab Immunology Lab

Institute for Virology

Cytomegalic Inclusion Disease (CID):a disease of the immunocompromised

Courtesy of G.JahnInstitute of Medical Virology

TuebingenJahn et al., Dtsch. Med. Wochenschrift, 1988

Congenital infection (in the US)

Cases per annum: 40,000Asymptomatic at birth: 36,000

5,400 Neurol. sequelaeSymptomatic at birth: 4,000

3,600 Neurol. sequelae 400 Fatal cases

CMV vaccine is 1 out of 7 ranked in level 1 out of 26 candidate vaccines included in the study

Annual gain of18,000 - 70,000 QALYs

Annual saving to the health systemUS $ 1.1 billion - 4.0 billion

Transplantation-associated (in the US)

Cases per annum: 2,800Moderate disease: 1,200Severe disease: 1,600

160 Fatal cases

IOM study: Vaccines for the 21st century

Immune senescence:A new indication for a CMV vaccine?

People aged 65 and older in the US ~ 40 millionCarriers of latent CMV ~ 30 million

Holtappels et al., JVI, 1998Podlech et al., JVI, 2000

Recipient

mCMV6 Gy

BMC

DonorBALB/c BALB/c

~

Immune surveillance of CMV in the murine BMT model

months

LungsAcute phase Latency

1

Viru

s

CD

8 T

cells

105

months


1

Viru

s

CD

8 T

cells

105

Recipient

mCMV6 Gy

BMC

DonorBALB/c BALB/c

~

Podlech et al., JVl, 2000

Inflammatory focus

Red staining of intranuclear IE1 proteinBlack staining of CD8 T cells

Control of acute CMV infection in the lungs

Podlech et al., JVI, 2000Holtappels et al., JVI, 1998; 2000

Recipient

mCMV6 Gy

BALB/c

~

Effector CD8 T cells• Activated phenotype CD62Llow

• Secrete IFN- • Lyse infected target cellsProtection upon adoptive transfer

Control of acute CMV infection in the lungs

CD8 T cell

months


1

Viru

s

CD

8 T

cells

105

Recipient

mCMV6 Gy

BMC

DonorBALB/c BALB/c

~

Effector-memory CD8 T cells

• Activated phenotype CD62Llow

• Secrete IFN- • Protect upon adoptive transfer

Persistence of protective CD8 T cell infiltrates during latency

~Episome

The immunodominant IE1 peptide of murine CMV

ORF Phase Sequence Restriction Reference

m123 (ie1) IE 168YPHFMPTNL176 Ld Reddehase, Rothbard, and Koszinowski, Nature, 1989

IFN- + IFN-

ERAAP

Presentation

ER

Golgi

CD8+

T cell

TAP

TCR

IE1

Processing andpresentation

of the IE1 peptide

Processing

For a review, see:Reddehase,Nature Rev. Immunol., 2002

Constitutiveproteasome

Immuno-proteasome


1V

irus

CD

8 T

cells

105

Enrichment of IE1 peptide-specific CD8 T cells during latency

1

3

M84

m18

m04

M83

m12

3/IE

1

4

5

M45

% E

LIS

PO

T-re

activ

e C

D8

T ce

lls

2

1

3

M84

m18

m04

M83

m12

3/IE

1

4

5

M45

%

ELI

SP

OT-

reac

tive

CD

8 T

cells

2

30.00012.000 3.000

60.000

mo

Holtappels et al.,J.Virol., 2000

Major Immediate-Early (MIE)region of mCMV

IE1 specific RT-PCR

P1/3 enhancer

1

ie1/3 transcription unit

M122 m123

Differential splicing

2345

235 1

234 1IE1 mRNA

IE3 mRNA

TFBS

Activation

What is the motor that drives the selective expansionof the IE1-specific CD8 T cells?

Selective and stochastic IE1gene expression during latency

Signal

Receptor

TF

IE1 specific RT-PCR

What is the motor that drives the selective expansionof the IE1 specific CD8 T cells?


P1/3 enhancer

1


M122 m123


2345

235 1

234 1IE1 mRNA

IE3 mRNA

TFBS

Activation

Signal

Receptor

TF


IE1 specific RT-PCR



P1/3 enhancer

1


M122 m123


2345

235 1

234 1IE1 mRNA

IE3 mRNA

TFBS

Activation

Signal

Receptor

TF


IE1 specific RT-PCR



P1/3 enhancer

1


M122 m123


2345

235 1

234 1IE1 mRNA

IE3 mRNA

TFBS

Activation

Signal

Receptor

TF


Poisson distribution analysisof variegated gene expression



P1/3 enhancer

1


M122 m123


2345

235 1

234 1IE1 mRNA

IE3 mRNA

TFBS

Activation

Signal

Receptor

TF


Kurz et al., JVI, 1999Grzimek et al., JVI, 2001Simon et al., JVI, 2005

Generation of recombinant CMV with a point mutation in thecodon of the C-terminal MHC anchor residue of the IE1 peptide

PYH

FM

PT

N A

GCALPY

HF

M PTN

CTA

234IE1

WT and revertant MHC class-I anchor mutant

L176A

A176L

Elimination of IE1 antigenicity enhances the frequencyof latency-associated IE1 transcription

Revertant Mutant

27

10

50

100 105

Inci

denc

e of

IE1

trans

crip

tion*

~

~

21

36

84

131

150

* 5 lungs

Simon et al., in preparation

IE1

Desilencing and immune sensing hypothesis

IE1-specificCD8 T cell


IE1

Desilencing and immune sensing hypothesis IE1-specificCD8 T cell



IE1

Desilencing and immune sensing hypothesis IE1-specificCD8 T cell


Effector function


Multiple checkpoints for immune sensing

Open viral chromatin structure at all essential loci

Abrogation of immune sensing by immunosuppression

MIE locus latency Stages of transcriptional reactivation Recurrence

IE1

anti-IE1 anti-X1 anti-Xn

Immunosuppression

MIE Locus

~

Conditions for virus recurrence:

How could latency-associated CMV gene expression contribute to immune senescence?

1. Cellular aging of clonotypic memory cells by a high number of cell divisions

2. Misallocation of immune system resources by clonal expansion of memory CD8 T cells specific for a single pathogen

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Immune Sensing of Latent Cytomegalovirus Reactivation: Impact on Immune Senescence?